1. Field of the Invention
The present invention relates to the field of jack stands.
2. Prior Art
Jack stands for the temporary support of an automobile are well known in the prior art. Such stands are normally used in conjunction with jacking devices, such as bumper jacks and axle jacks, for supporting a vehicle or at least a portion thereof with one or more wheels off of the ground.
In their simplest application the axle or frame of a vehicle is raised by some form of conventional jack, and a jack stand is adjusted to the appropriate height and placed under the frame or axle so as to retain the vehicle at the desired height and to allow the removal of the jack for other use. Thus in this application the primary function of the jack stand is to support the vehicle at the desired height, so that the features of adjustability and positive locking of the stand at the selected height are primary considerations.
Whenever jack stands are used to support a vehicle so that two or more wheels are off the ground, typically the two front wheels or the two rear wheels, the further requirements of strength and rigidity of the jack stand also become very important. In particular, with the two front wheels or the two rear wheels supported off the ground, the directional stability normally present with three wheels on the ground is lost, even with the remaining two wheels locked, so that the stability of the support depends to a large extent upon the stability of the jack stand, which in turn depends upon the combination of the base size and strength and rigidity of the base support assembly. In particular, a narrow base or small "footprint" of a jack stand will decrease its stability, presenting a safety hazard when supporting a vehicle. In fact jack stands have come into widespread use in recent years not only because they are less expensive than ordinary jacks and free jacks for other use, but also because they have much larger base areas than conventional jacks, grossly reducing the likelihood of the tipping and loss of support. Jack stands also have the advantage of being relatively solid and positive in their vertical support, unlike conventional jacks which may slip or may be inadvertently released, to the great hazard to those depending upon the support.
Also in recent years jack stands have found their way into the consumer market and are now widely distributed for consumer use, being sold in auto parts stores, hardware stores and the like, for supporting vehicles, boat trailers, camping trailers, etc. For this market, cost is a primary consideration, requiring that the foregoing objects be achieved with a simple assembly of a minimum number of parts.
In general, prior art jack stands utilize a simple straight shank pin for vertical height adjustment, and thus do not have any means for locking the pin in position.
One prior art jack stand having a locking device is disclosed in U.S. Pat. No. 2,439,854. The device of that patent utilizes a conventional jack stand having circular through holes in the tubular members, with a pin having three right angle bends providing engagement with the stand when in a lower position to resist withdrawal. Other locking devices are also shown in U.S. Pat. Nos. 872,335 and 2,685,353.